Mirrored pose problem (IK goes crazy)
After take a look into your Blender's file. I think that your problem is about your Leg Control bones aren't have the same local rotation in edit mode. So whenever you do mirror paste, your bone will move at wrong direction.
How to fix it:  


Select your armature then press TAB to enter Edit Mode  
Select both of your Leg Control bones then press CTRL + N and choose Global + Z Axis

Back to Pose Mode and do your mirror paste, the rig is working perfectly now.



P/S: You must re-animate your animation, because after reset rotation, your armature doesn't work correctly with current animation. Here is your file after i fix it. Sorry about my bad english, hope someone could edit this :(